Oil drain plug size

[Sprocket]

Is there a variation in oil drain bolt sizes?

Bought a washer online described for F0/77, took out leaky dowty style washer, plugged hole with finger, struggled to get old washer off plug one-handed, eventually 7 year old mini-me helped, but then realised the new washer I have is way too small to go on. Reassembled and washed (thankfully unsullied) oil off my hands and scratched head.

Mine is an early engine. I can only think the bolt sizes changed, or someone has already mullered my sump and it's a bigger bolt in there.

[Deano400]

Should be 12mm for all years as far as I know.

[Trigger]

As Deano said, all are the same at 12mm 

[Sprocket]

Cheers  Oil out then, investigate what on earth has been done on my sump. Sigh.

[Laverda Dave]

There may not be a problem with your sump. I bought a new sump bolt with a magnetic tip online for my 400/4. When I came to fit it I thought the thread pitch looked incorrect so I matched it up against my old bolt to find it was too coarse! Had I fitted it without checking first I would have stripped the sump thread!
There are an awful lot of parts advertised as fitting our bikes that dont! I had a similar issues when I bought a s/s caliper bleed nipple, a carb rebuild kit, bulbs, brake pistons etc........retailers on ebay in particular just say parts fit to shift stock.
My local Honda dealer keeps the sump washers in stock as they use so many of them.
Does your existing sump bolt have a 17mm socket head?

[Nurse Julie]

I'm a bit confused (easily achievable). Have you not just stripped and rebuilt the engine? Did you fully clean the sump pan by removing oil separation plate? If it's the wrong sump bolt, which makes sense as there shouldn't be a dowty washer there anyway, did you not notice any damage / repair / bodge around the area?

[Sprocket]

I'm a bit confused (easily achievable). Have you not just stripped and rebuilt the engine? Did you fully clean the sump pan by removing oil separation plate? If it's the wrong sump bolt, which makes sense as there shouldn't be a dowty washer there anyway, did you not notice any damage / repair / bodge around the area?

Haha of course I noticed it. But pay attention, and check against other engines? No.  The sump has had a repair, it's been welded and I did a small amount of smoothing before I sent it off for cleaning. But the threads looked good and I assumed it wasn't leaking, as there wasn't a pool of oil on the garage floor before I took it all apart.

The bolt I have is about a 22mm (from memory) head, the thread looks to be about 15mm (I measured this so I could get a copper washer that might fit from the local fastenings place).

Bottom line is that I will have to get an unbuggered sump for the girl when I can prove it runs.

[Laverda Dave]

DSS has replica sump pans for £95+VAT+post and you'll need the bolt and washer (he sells those as well).

[mike the bike]

It's 17mm.

[Sprocket]

So the head is 24mm, and quite clearly you can see the crack (now it's wet!) the PO has fixed. The sump doesn't leak, the reason this is soggy is because I undid it to measure the size of the thread. I think I'll keep as-is now and get a replacement sump in time for the first oil change.

[TrickyMicky]

Regarding the comment made about fitting a sump plug with a magnetic tip, I was advised many years ago to avoid these like the plague. Normal wear and tear in an engine will produce minute metallic swarf which should be held by the oil filter, the problem with the magnetic plugs is that they attract the swarf into one lump and if that should become loosened then you have a rather large lump of metal rubbish travelling round your engine. In later years when I worked for a car gearbox re-conditioning firm, after stripping out the innards of the old boxes, we were instructed to throw away the magnets which were often fitted in the base of the box for the very same reason.